These trees truly are giants of the forest.In Spain, the man called Magellan was provisioning his ships for what would be the first time anyone would ever sail around our world. On the other side of the planet, deep in a forest in what is now known as Western Australia, a seed dropped from a massive tree onto the carpet of gum leaves beneath.

Magellan never made it back in person, but his fleet sailed triumphally back to Spain, and changed the world. By that time, the seed had germinated, sprung roots, and was busy growing into a sapling reaching for the forest canopy 80 metres above. Since then, billions of people have travelled round the world. Dynasties, kingdoms, inventions and global wars have utterly changed our environment. But the same tree, well over 400 years old now, is still standing, flowering once every four years to complete the cycle of life it started seven generations ago.

Experience the forest canopy just as it was 400 years ago.The tree is the Red Tingle (eucalyptus jacksonii), which traces its origins back to the prehistoric forests of Gondwanaland, one of the original continents which split apart to form Australia some 50 million years ago. Originally born in the wet and temperate climate that covered many parts of Australia, the Red Tingle has clung on in this tiny patch, confined to about 6,000 hectares of native forest and nowhere else in the world.

"The problem was that in the 1980s, people started to realise what a treasure these trees were, and started hiking into what we now call the Valley of the Giants," says Julie Ross, Business Manager at the Walpole Nornalup National Park, WA. "Increasing numbers of visitors began erode the normal habitat, to upset the drainage and underforest composition, with the result that some of the bigger trees died and fell."

The WA government, through its National Parks arm, decided this unique natural feature needed urgent protection but one that would still allow visitors to see the huge gum trees and their unique hollow trunks, in some cases big enough for people to shelter in.

The solution was to build a series of treetop-high 60 metre walkways that gradually take visitors to the forest canopy 40 metres above the now-protected forest floor. Now 12 years old, it has taken nearly 2.5 million people into intimate contact with the Red Tingles, but with no harm to their environment - only five square metres of the forest was cleared to build the walkway.

Trees that grow 80m high need natural buttresses."Building the walk saved many of these trees," says Tom, one of the park rangers. "They have relatively shallow roots, which spread as they grow older, resulting in the unique buttressed trunk that gets hollowed out at the bottom by fungi, insects and fire. If walkers had carried on coming here and disturbing the area round the base of the trees too much, it would have ruined the root system and endangered the health and stability of the trees they had come to see."

Now, thanks to the Tree Top Walk, some 200-300,000 people a year enjoy the unique calm of this deep and ancient forest, and sound of the wind whispering in gum leaves. Exactly the same sound that Magellan would have heard if he had taken a different route and landed in WA about 450 years ago.

Even forest giants start off as saplings.Getting there:

The Valley of the Giants is about five hours (400km) drive south of Perth, capital of Western Australia (WA) with its international airport. Hiring a car is the best way to get there; rental cars range from A$50-80 a day.